summercms/modules/pier/guard_rules_test.go

package pier_test

import (
	"context"
	"errors"
	"net/http"
	"slices"
	"strings"
	"testing"
	"time"

	"git.golem15.com/golem15/summercms/modules/pact"
	"git.golem15.com/golem15/summercms/modules/party"
)

// permGuard parses acme.perm:<code> middleware into required permission
// codes and allows a subject only when its granted codes cover the route's
// codes and the tool's (the union, D-16).
func permGuard(granted map[uint][]string) *fakeGuard {
	return &fakeGuard{
		parse: func(mw []string) (pact.MCPRequirements, error) {
			var req pact.MCPRequirements
			for _, m := range mw {
				if code, ok := strings.CutPrefix(m, "acme.perm:"); ok {
					if code == "" {
						return pact.MCPRequirements{}, errors.New("acme.perm names no code")
					}
					req.Permissions = append(req.Permissions, code)
				}
			}
			return req, nil
		},
		allow: func(s pact.MCPSubject, req pact.MCPRequirements, perms []string) bool {
			for _, code := range append(slices.Clone(req.Permissions), perms...) {
				if !slices.Contains(granted[s.UserID], code) {
					return false
				}
			}
			return true
		},
	}
}

// methodDenyGuard is a method-aware provider that refuses one method, as an
// admin token whose scopes allow GET only does.
type methodDenyGuard struct {
	methodGuard
	deny string
}

func (g methodDenyGuard) MCPAllowsMethod(ctx context.Context, s pact.MCPSubject, req pact.MCPRequirements, perms []string, method string) (bool, error) {
	ok, err := g.methodGuard.MCPAllowsMethod(ctx, s, req, perms, method)
	return ok && method != g.deny, err
}

// TestGuardRules (D-15, D-16, D-22): the route's middleware requirements and
// the tool's Permissions are both handed to the provider (the union decides);
// a provider that rejects a route's middleware fails boot; a route the
// provider does not call token-guarded binds only with a declared Guard; a
// method-aware provider is asked with each tool's own method, so a GET-only
// scope hides write tools (the built-in backend provider does this with
// cabana.ScopeLimitFor, pinned by cabana's TestScopeLimitForMethods).
func TestGuardRules(t *testing.T) {
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()
	rules := testRoute{method: http.MethodGet, path: "/rules/a", mw: []string{"acme.auth", "acme.perm:p.a"}, h: noContent}

	t.Run("requirements union with tool permissions", func(t *testing.T) {
		guard := permGuard(map[uint][]string{7: {"p.a", "p.b"}, 8: {"p.a"}})
		plugin := routePlugin{id: "test.rules", factory: "acme.perm", routes: []testRoute{rules},
			tools: []pact.MCPTool{
				{Name: "both", Method: "GET", Path: "/rules/a", Input: struct{}{}, Permissions: []string{"p.b"}},
			}}
		plain := routePlugin{id: "test.plain", guard: "plain", routes: []testRoute{{method: http.MethodGet, path: "/rules/plain", mw: []string{"acme.auth", "acme.perm:p.a"}, h: noContent}},
			tools: []pact.MCPTool{{Name: "route_only", Guard: "acme", Method: "GET", Path: "/rules/plain", Input: struct{}{}}}}
		in := startInstance(t, newApp(t, appSpec{guards: []pact.MCPGuard{guard}}), plugin, plain)
		if got := listNames(t, ctx, sdkClient(t, ctx, in.url(), "oas_at_test", clientOpts{})); !slices.Equal(got, []string{"plain_route_only", "rules_both"}) {
			t.Fatalf("user 7 (p.a, p.b) lists %v", got)
		}
		if got := listNames(t, ctx, sdkClient(t, ctx, in.url(), "oas_at_other", clientOpts{})); !slices.Equal(got, []string{"plain_route_only"}) {
			t.Fatalf("user 8 (p.a) lists %v", got)
		}
		var saw bool
		for _, c := range guard.recorded() {
			if slices.Equal(c.req.Permissions, []string{"p.a"}) && slices.Equal(c.perms, []string{"p.b"}) {
				saw = true
			}
		}
		if !saw {
			t.Fatalf("the provider never saw the route's p.a with the tool's p.b: %+v", guard.recorded())
		}
	})

	t.Run("rejected middleware fails boot", func(t *testing.T) {
		guard := permGuard(nil)
		bad := routePlugin{id: "test.rules", factory: "acme.perm", routes: []testRoute{{method: http.MethodGet, path: "/rules/bad", mw: []string{"acme.auth", "acme.perm:"}, h: noContent}},
			tools: []pact.MCPTool{{Name: "bad", Method: "GET", Path: "/rules/bad", Input: struct{}{}}}}
		_, err := mountPier(t, newApp(t, appSpec{guards: []pact.MCPGuard{guard}}), []party.Plugin{bad})
		if err == nil || !strings.Contains(err.Error(), "rejects the route's middleware") || !strings.Contains(err.Error(), "names no code") {
			t.Fatalf("err = %v", err)
		}
	})

	t.Run("not token-guarded needs a declared guard", func(t *testing.T) {
		guard := &fakeGuard{notToken: true}
		route := testRoute{method: http.MethodGet, path: "/rules/session", mw: []string{"acme.auth"}, h: noContent}
		implicit := routePlugin{id: "test.rules", routes: []testRoute{route}, tools: []pact.MCPTool{{Name: "s", Method: "GET", Path: "/rules/session", Input: struct{}{}}}}
		if _, err := mountPier(t, newApp(t, appSpec{guards: []pact.MCPGuard{guard}}), []party.Plugin{implicit}); err == nil || !strings.Contains(err.Error(), "not token-guarded") {
			t.Fatalf("implicit binding: err = %v", err)
		}
		declared := implicit
		declared.tools = []pact.MCPTool{{Name: "s", Guard: "acme", Method: "GET", Path: "/rules/session", Input: struct{}{}}}
		if _, err := mountPier(t, newApp(t, appSpec{guards: []pact.MCPGuard{&fakeGuard{notToken: true}}}), []party.Plugin{declared}); err != nil {
			t.Fatalf("declared guard: %v", err)
		}
	})

	t.Run("method-aware provider sees each tool's method", func(t *testing.T) {
		guard := methodDenyGuard{methodGuard: methodGuard{fakeGuard: &fakeGuard{}}, deny: http.MethodPost}
		plugin := routePlugin{id: "test.rules",
			routes: []testRoute{guarded(http.MethodGet, "/rules/items"), guarded(http.MethodPost, "/rules/items")},
			tools: []pact.MCPTool{
				{Name: "list", Method: "GET", Path: "/rules/items", Input: struct{}{}},
				{Name: "create", Method: "POST", Path: "/rules/items", Input: struct{}{}},
			}}
		in := startInstance(t, newApp(t, appSpec{guards: []pact.MCPGuard{guard}}), plugin)
		if got := listNames(t, ctx, sdkClient(t, ctx, in.url(), "oas_at_test", clientOpts{})); !slices.Equal(got, []string{"rules_list"}) {
			t.Fatalf("lists %v, want the GET tool only", got)
		}
		methods := map[string]bool{}
		for _, c := range guard.recorded() {
			methods[c.method] = true
		}
		if !methods[http.MethodGet] || !methods[http.MethodPost] || methods[""] {
			t.Fatalf("provider asked with methods %v", methods)
		}
	})
}